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Homework Help: Energy Work Problem, all algebra

  1. Apr 13, 2010 #1
    1. The problem statement, all variables and given/known data

    A small block is placed at height h on a frictionless ramp inclined at an angle theta. Upon being released, the block slides down the ramp and then falls to the floor (a distance y below the base of the ramp). A small hole is located a horizontal distance x from the end of the ramp.

    From what height, h , should the block be released in order to land in the hole? Note: that the unknowns for this problem are x, y, and theta. Your answer should be an algebraic expression that starts with h=


    2. Relevant equations



    3. The attempt at a solution

    I started out by using the fact that
    mg(h+y)=(1/2)mv^2
    working it out to
    h= (v^2/2g)-Y

    my issue is finding v^2, I know that (2gh)^1/2 is the final velocity for both mgh and mgy.. I need to eliminate the h somehow because it is on both sides, but I am unsure how to do so. I have used trig, but am having no luck. I already solved this problem once using kinematics, and found it to be much easier. Any help solving this with energy would be appreciated.
     
  2. jcsd
  3. Apr 13, 2010 #2

    tiny-tim

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    Homework Helper

    Welcome to PF!

    Hi enkerecz! Welcome to PF! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    (how did you manage to solve this without using x ? :confused:)

    I don't think energy will give you anything more than the velocity on leaving the ramp: after that, you will have to use the standard constant acceleration equations. :smile:
     
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